Understanding how reionization occurred, the nature of the early sources that drove it, the thermal history and fine-grained properties of hydrogen
gas in the cosmic web, and how to extract crucial information on the cosmological model from observations of Lyman-\(\alpha \)  absorption are among the most
important open questions in cosmology and key science drivers for numerous major new instruments and facilities. The promise of the Lyman-\(\alpha \)  forest
for constraining cosmological physics including the nature of dark matter and dark energy has
motivated in part the construction of the Dark Energy
Spectroscopic Instrument [1]},
which measures
absorption line spectra backlit by nearly a million quasars at \(z>2\) . Interpreting such
observations requires detailed cosmological hydrodynamical simulations that cover an extensive range of uncertain photoionization and photoheating
histories and consistently maintain high resolution throughout a statistically representative sub-volume of the Universe.
